Steam generator systems can include a once-through steam generator and water treatment system to provide purified water to the steam generator. If hard water or produced water from a hydrocarbon recovery system is used in the steam generator, impurities in the water can cause fouling and damage to the components and plumbing. Water treatment systems have a tendency to concentrate impurities over time and require substantial space, capital cost and energy consumption. Additionally, steam generator systems are highly inefficient with respect to the amount of clean water produced from a given amount of unclean water input into the water treatment system.